The present invention relates to cut-off blades for cutting sheet material and to such cut-off blades used on dispensers that have sharp cutting edges defined by spaced projecting teeth that are adapted for transversely cutting dispensed lengths of the sheet materials from supplies of the sheet materials carried by the dispensers.
The art is replete with dispensers including cut-off blades having sharp cutting edges adapted for transversely cutting dispensed lengths of sheet materials from supplies of the sheet materials carried by the dispensers. U.S. Pat. Nos. 3,567,557, 4,096,021, and 4,915,768 provide illustrative examples. The cut-off blades on some of those dispensers provide a potential source of injury for persons using the dispensers, particularly if the cut-off blades have sharp spaced projecting teeth such as those on a cut-off blade described in U.S. Pat. No. 4,913,767 that is adapted to pierce and cut folded polymeric sheet material. A guard described in U.S. Pat. No. 4,989,769 can be provided for such a cut-off blade, however, such guards must be moved from over the cut-off blade before the blade can be used to cut, which can be a slight inconvenience. Such moveable blade guards have been removed by workmen that are less concerned with safety than with the ease of using the dispenser. International Application WO 98/51603 discloses other, less easily removable but generally more complex structures for transversely cutting dispensed lengths of sheet materials from supplies of the sheet materials carried on dispensers. Those structures protect a user of the dispenser from a cutting member or cut-off blade between its uses to cut sheet material by moving the cut-off blade to a position where it will not be easily contacted by a person handling the dispenser, while affording convenient movement of the cut-off blade to a cutting position that affords easy efficient severing of the sheet materials when that is desired.
The present invention provides a cut-off blade assembly that is useful on dispensers of the types described above for transversely cutting dispensed lengths of sheet materials; which cut-off blade assembly affords easy efficient severing of the sheet material including folded polymeric sheet material, involves no moving parts, and yet provides significant protection to a user of the dispenser against injury caused by accidental contact with the cut-off blade assembly.
The cut-off blade assembly according to the present invention comprises a thin metal blade including an attachment portion by which the cut-off blade assembly can be attached to a dispenser, and a plurality of projecting similarly shaped triangular primary teeth. The teeth each have two sides terminating in points and have bases adjacent the attachment portion that are aligned in a first direction along the blade so that their points project generally at right angles to that first direction. Edge surfaces on the sides and at the points of the primary teeth intersect a major surface of the teeth at an included angle of no greater than about 90 degrees to define at least a portion of a cutting edge for the blade at that intersection. The cut-off blade assembly further includes projections along one major surface of the primary teeth. Those projections have distal ends positioned adjacent the points of the teeth (e.g., spaced about 0.01 inch or 0.025 centimeter away from the points along the primary teeth), have sufficient thickness at the points in a direction normal to the major surfaces of the teeth to restrict contact between a person and the cutting edge on the points of the primary teeth, and are shaped and positioned so that they extend only along the primary teeth to afford easy cutting of sheet material pressed against the cutting edge of the blade and free movement of the end of the sheet material being cut over the primary teeth.
The sides of adjacent primary teeth can intersect at the bases of the adjacent primary teeth to define a generally V shaped opening therebetween, or the adjacent primary teeth can be spaced appart and the blade can include portions (e.g., a plurality of (e.g., 4 or 5) recessed smaller secondary teeth) defining parts of the cutting edge for the blade between the adjacent primary teeth.
Such use of projections to restrict contact of a person with the cutting edge at the points on the primary teeth provides significant protection for a user of the dispenser on which the cut-off blade assembly is mounted. Those points are the parts of the blade that can make inadvertent contact with a persons flesh; whereas the recessed portions of the cutting edge along edges of the primary teeth between their points and along recessed portions of the blade (if any) beween primary teeth spaced up to about 0.4 inch or 1 centimeter appart will typically not make contact with a persons flesh if the projections restrict the points of the primary teeth from becoming imbeded in it. If a person using the cut-off blade assembly accidentally forces his flesh against its cutting edge, the projections on the primary teeth push his skin away, thereby preventing or minimizing penetration of his skin by the blade and limiting any injury that may be sustained to a scratch or shallow cut; whereas the same contact with the blade without the projections could result in a cut requireing medical attention.
The thickness of the projections at the points should be at least 0.02 inch or 0.05 centimeter thick to provide a measure of safety for the user, and preferably the projections are about 0.03 inch or 0.07 centimeter thick at their points which provides a good combination of safety for the user with ease of cutting of sheet material by the cut-off blade assembly.
The projections can project from a base portion of a layer of material in which the projections are included. The base portion can then be attached along the surface of the blade with the projections projecting over the primary teeth.
The cut-off blade assembly is, for example, useful on the type of dispenser called a masking machine or device, one embodiment of which is described in U.S. Pat. No. 4,990,214.